Heat exchanger

ABSTRACT

A heat exchanger consists of a stack of rectangular corrugated plates whose corrugations run at angles of 45* to the longitudinal sides of the plates with bent edges of pairs of adjoining plates sealed together to define respective flow compartments for the heat exchange fluids. Each pair of contacting plates is rotated through 180* with respect to the adjoining plate so that the corrugations cross one another. Between the plates whose bent edges are turned toward one another, stacks of similarly corrugated plates are provided to constitute a regenerative heat exchange packing or heat-storage reservoir.

Unite States Patent 1 Nasser et al.

[111 3,759,322 [451 Sept. 18,1973

1 1 HEAT EXCHANGER [75] Inventors: Gamal El Din Nasser, P1anegg;llans Waldmann, Olfratsliausen, both of Germany [73] Assignee: Linde Alttiengesellschaft,

Wiesbaden, Germany 221 Filed: Sept. 17, 1971 211 Appl. No.: 181,518

[30] Foreign Application Priority Data Oct. 1, 1971 Germany P 20 48 386.7

52 US. Cl. 165/166 [51] Int. Cl F281 3/00 [58} Field of Search 165/166, 167

[56] References Cited UNITED STATES PATENTS 3,240,268 3/1966 Armes 165/167 3,568,765 3/1971 Konrad 165/166 10/1969 Tlotenbucher 7/1971 Duncan Primary Examiner-Charles J. Myhre Assistant Examiner-Theophil W. Streule, Jr. Attorney-Karl F. Ross [57] ABSTRACT A heat exchanger consists of a stack of rectangular corrugated plates whose corrugations run at angles of 45 to the longitudinal sides of the plates with bent edges of pairs of adjoining plates sealed together to define respective flow compartments for the heat exchange fluids. Each pair of contacting plates is rotated through 180 with respect to the adjoining plate so that the corrugations cross one another. Between the plates whose bent edges are turned toward one anothenstacks of similarly corrugated plates are provided to constitute a regenerative heat exchange packing or heat-storage reservoir.

7 Claims, 6 Drawing Figures A AE LA' i, ,7 I V I' I 1 4 5 Sheets-Sheet l Patented Sept. 18, 1973 AMAL L IN NASSER FIANS \EALDRAANN INVENTORS BY m l i205;

ATTORNEY Patented Sept. 18, 1973 3,759,322

5 Sheets-Sheet 2 F|G.2 o21 H1022 l2 FIG.6

GAMAL EL DIN NASSER HANS WALDMANN INVENTORS Kar gloss ATTORNEY Patented Sept. 18, 1973 3,759,322

5 Sheets-Sheet 3 FIG.3

GAMAL EL 0m NASSER HANS WALDMANN lNVENTORS ATTORNEY Patented Sept. 18, 1973 5 Sheets-Sheet 4 R E S S A N I 2 T 5 NM 6 M @1 m w LA 8 l m, "T mm AA 4 H 6 lllilllllllllulp. Q T a AAA 6 T w v T i v 2 v 1 T i l V e m A q y J w J A l v 7 a: m 6

ATTORNEY Patent ed Sept. 18, 1973 5 Sheets-Sheet 5 GAMAL EL DIN NASSER HANS WALDMANN INVENTORS.

BY ma 720s;

ATTORNEY HEAT EXCHANGER CROSS-REFERENCE TO RELATED APPLICATIONS FIELD OF THE INVENTION The instant application relates to heat-exchanger structures for the effective transfer of heat among two or more fluids and, more particularly, to a heat exchanger operating at least in part on regenerative principles.

BACKGROUND OF THE INVENTION Plate-type heat exchangers, in which pairs of adjacent plates define flow chambers for one or more fluids adapted to traverse the stack of plates between a fluid outlet and a fluid inlet are well known in the art as a distinct type of heat exchanger, to be compared or contrasted with tube-nest heat-exchangers and tubebundle heat exchangers. In plate-type heat exchangers, moreover, it has been proposed to provide corrugated plates or to deform the plates more or less uniformly in order to promote turbulence and increase the heattransfer rate from one fluid to the other through the plate-like wall separating the respective flow compartments. For the most part, plate-type heat exchangers of conventional construction are expensive, have insufficient heat-exchange efficiency and cannot be assembled conveniently. Furthermore, they may be characterized by a lack of versatility for numerous fluids and methods of heat transfer.

At this point, we should mention that numerous modes of heat transfer are common in the art. In direct heat exchange, for example, one heat-transfer fluid may be passed in counter-current to the other (e.g. when the first is a rising gas and the second is a descending curtain of liquid) so that the heat of the former is transferred to the latter by direct contact and without any intermittent heat storage or without any conductive transfer between them. In one indirect heat-transfer technique, one heat-exchange fluid is passed through a flow compartment of a heatexchanger defined by a thermally conductive wall which simultaneously is contacted on the opposite side by a second heat-transfer fluid. Although the transfer of heat to the wall by the warmer fluid and the absorp tion of heat from the wall by the cooler fluid takes place simultaneously, the transfer is nevertheless indirect since it requires the intermediary of the wall. In this case, the wall prevents mixing of the fluids but allows heat transfer from one to the other. In another in direct heat-exchange mode, a heat-storage reservoir is provided in the heat exchanger and may be contacted with a relatively warm fluid to raise the temperature of the mass and subsequently by a relatively cool fluid to abstract heat from the mass. The abstraction of heat from the mass may be considered a storage of cold therein, the cold being transferred to a relativelyv warm fluid at the start of the mixed cycle. The latter heat-exchange mode is often termed regenerative, since the transfer from one fluid to the other takes place via a thermal storage reservoir and in two distinct phases separated in time. Frequently it is desirable to use a heat exchanger for simultaneous indirect heat exchange and regenerative heat exchange, for a larger number of fluids than most conventional heat exchangers can successfully employ, and with high heatexchange efficiency and low capital cost.

OBJECTS OF THE INVENTION It is an object of the invention to provide an improved heat exchanger wherein the aforementioned disadvantages are avoided.

It is also an object of the invention to provide a lowcost, highly versatile, easily assembled and high efficiency heat exchanger.

SUMMARY OF THE INVENTION These objects, and others which will become apparent hereinafter, are attained in accordance with the invention with a heat exchanger comprising a stack of rectangular corrugated plates whose corrugations run at angles of 45 to the longitudinal and transverse sides of the plates. The latter have inwardly bent (quarterround) edges sealed to the edges of adjoining plates with the thus-paired plates in back-to-back relationship with the adjacent pairs. Each pair of contacting plates is rotated (spatially) through l with respect to the alternating therewith so that the corrugation arrays are mutually crossing on mutually adjacent plates. Between the plates whose bent edges are turned toward one another, stacks of similarly corrugated plates are provided in spaced relationship to constitute a regenerative heat-exchanger packing.

In accordance with the invention and with principles defined in application Ser. No. 773,082 and application Ser. No. 45,976 mentioned earlier, heat-exchanger compartments are created by welding, soldering or otherwise sealing together the mutually confronting lips or edges of a pair of corrugated sheet-metal plates, the plates being spaced from one another to defined one compartment and define with other plates one or more additional compartments.

More specifically, application Ser. No. 773,082 provides a heat exchanger in which the corrugated plates form tube bundles. Thus, each pair of tube plates lying in planes parallel to the array of mutually parallel tubes to be formed therebetween has, on confronting sides,

a plurality of spaced-apart confronting concavities or corrugations which mutually register to constitute the respective tubes between them. The relatively thin-wall plates are preferably formed with the respective concavities by deformation of the plates in the manner or corrugations with each concavity extending over an arc segment of about The concavities are separated by webs which lie in a diametral plane of the array and are generally planar so as to be coextensive with the corresponding webs of the confronting plate. These ribs, when each pair of plates is assembled with the plates in mutually confronting relationship, form the reinforcing ribs between each pair of tubes of the particular array. The tubular members are constituted by semi-cylindrical corrugation troughs which, as noted, register with the troughs of the oppositely facing plate. The plates are generally rectangular in plan view but are formed at their small sides or ends with outwardly flared or bent quarter-round flanges or marginal portions which are welded to the outwardly turned corresponding flanges of neighboring plates of adjacent arrays. The interconnected flanges thus form end walls or bottoms of the chamber between the tubes of the arrays. The longitudinal edges of the plates of each array, which run parallel to the corrugations and thus to the tubes constituted thereby, are welded together.

In the application Ser. No. 45,976, filed by us jointly, similar principles apply. in this system the heat exchanger basically comprises a cylindrical casing having a vertical axis and a prismatic heat-exchange body havin g at least four surfaces lying along chords or the cyllnder and defining chambers and ducts therewith which communicate with the body of the heat-exchanger unit. The prismatic assembly consists of a plurality of parallel arrays of parallel passages, each array of passages being defined between a pair of plates formed with confronting semi-cylindricai cavities which register to provide tubes of circular cross-section. The spaces between the pair of plates and the tube arrays define inner compartments which are closed at top and bottom by outwardly flared flanges or marginal portions of the plates defining each tube array and butt-welded together along horizontal seams. The plates are so constructed and arranged as to be of identical geometric configuration but are rotated relative to one another through 180 about an axis parallel to the plane of the plate whereby only a single type of plate need be used.

One of the objects of the present invention, briefly described above, is to extend the principles originally set forth in the commonly assigned copending application mentioned above to provide a heat exchanger of improved efficiency and quality and of reduced assembling and capital costs.

The present invention is also intended to provide a heat-storage or cold-storage capacity in a plate-type heat exchanger of the kind described generally above and in the afore-mentioned copending applications, to provide a heat-exchanger structure which is capable of withstanding elevated pressures without significant distortion and without excessively thick plates, to provide a regenerative heat exchanger adapted to be traversed by pure fluids without contamination as well as by relatively impure fluids capable of precipitating components in the regenerator sections, and to provide a simplified high-efficiency transfer of heat among two or more fluids.

To this end, the heat exchanger of the present invention comprises a stack of pairs of primary plates, the plates of each pair being sealed together along at least some of their edges and being generally coextensive to define fluid compartments between them. The pairs of plates are, in turn, stacked in pressure-transmitting relationship with one another to define additional flow cross-sections for one or more fluids, while within the compartments defined between the plates of each pair there are provided secondary stacks of plates in spaced-apart relationship along the direction of fluid flow and in force-transmitting relationship among themselves and the walls of the compartment between which they are sandwiched. The primary plates as well as the secondary plates are preferably provided with arrays of parallel corrugations or like formations or protuberances which engage other plates at numerous contact points substantially uniformly distributed over the areas of the plates. Since the stacks of secondary plates resist inward deformation of the primary plates between which they are sandwiched and the primary plates of each pair bear in force-transmitting relationship on similar pairs of primary plates, the entire assembly is resistant to compression or expansion forces resulting from gas pressure differentials across the plates. The primary plates of each pair advantageously are of identical geometrical configuration but are rotated one with respect to another about an axis in the main flow direction or parallel to an edge of the generally rectangular plates. Furthermore, the plates of the secondary stacks may be of identical geometrical configuration and are coextensive while also being rotated, one with respect to another, through about an axis parallel to the fluid-flow direction or a longitudinal edge. in this way, the corrugations of mutually abutting plates each lying at an angle to the edges cross one another so that contact points are defined by each crossing.

The spaced-apart secondary stack of plates form heat-storage means for alternately storing heat or cold and transferring heat or cold to the next fluid passing through the compartments between the paired plates. The system just described has, inter alia, the advantage that the heat-storage masses are formed by plates geometrically similar to those used for the concurrent indirect heat exchange between fluids traversing compartments separated by these plates. Construction of the heat exchanger is thereby greatly simplified and made less expensive.

According to a more specific feature of the invention, all of the plates have similar corrugations oriented at the same angle to the longitudinal and traverse edges of the plates, preferably an angle-of 45, so that the crossover points or contact points are defined between corrugations lying at right angles to one another. The heat exchanger of the present invention finds considerable utility where a reversing type of operation is to be carried out. In these cases, the regenerative portion of the heat exchanger is alternately supplied with a relatively warm impure fluid from which undesired components can be precipitated as the fluid contacts the previously cooled heat-storage mass. A sparging gas may then be fed through the regenerator compartments to remove these residues during the next half-cycle. Typical of a heat exchanger for this purpose are the heat exchangers which are required in air-rectification installations. In such installations, a raw gas, usually air, is cooled by passage through a regenerator flow crosssection and deposits relatively high-boiling-point components such as water vapor and carbon dioxide therein. The cold required for the purpose is drawn from one or more relatively pure gases of the rectification installation, namely oxygen or nitrogen, which may be passed through heat-exchanger compartments traversed only by these high-purity components and hence free from the danger of contamination. When the cold is abstracted from the heat-storage mass, a sparging gas can be passed through the compartment to remove the deposited impurities. The system of the present invention is especially advantageous in that it can be used for this purpose.

Thus another feature of the present invention resides in the provision of a regenerative heat exchanger with reversible and interchangeable functions of the several compartments. The heat exchanger thus includes at least one, but preferably a plurality of regenerator compartments containing secondary stacks of plates and interchangeable in function for the alternate passage of a raw gas such as air or an impure rectification product such as impure nitrogen, and a sparging gas or some other gas residue designed to flush impurities from this compartment. The compartments between pairs of primary plates may then be used only for the passage of pure components such as pure oxygen and pure nitrogen.

We have found, in practice, that for given quantities, pressure drops and heat-transfer characteristics, the heat exchanger of the present invention can be made much more simply and inexpensively than tube-coil, tube-bundle, packed-column and like heat exchangers as have conventionally been used heretofore for air rectification purposes. Moreover, the thickness of the plates, spacing, corrugation depth, configuration and width can be adjusted to vary the mass of the heatstorage members and thus provide optimum results from a thermodynamic viewpoint. Since each plate is supported at numerous contact points against each adjacent plate, high pressures may be accommodated. To reduce conductive heat transfer in the fluid-flow direction, we also prefer to make the heat-storage stacks relatively short and to provide narrow gaps between them.

DESCRIPTION OF THE DRAWING The above and other objects, features and advantages of the present invention will become more readily apparent from the following description, reference being made to the accompanying drawing in which:

FIG. 1 is a portion of a longitudinal cross-section through a stack of heat-exchanger plates according to the invention and corresponding to a section along line I I of FIG. 3;

FIG. 2 is another fragmentary cross-sectional view, in plan, taken along the line II II of FIG. 4;

FIG. 3 is a partial cross-section taken into different horizontal planes generally along the line III III of FIG. 4;

FIG. 4 is a view partly in elevation and partly in sectionalong the line IV IV of FIG. 5 of a heat exchanger according to the invention;

FIG. 5 is a cross-sectional view orthogonal to the section of FIG. 4 and taken generally along the line V V thereof; and

FIG. 6 is a perspective view illustrating one portion of a plate embodying the invention.

SPECIFIC DESCRIPTION In the following description, similar or identical reference numerals will represent elements having identical functions and structures although they may be assembled differently from one embodiment to the next.

Before discussing the structure illustrated in FIGS. 15, reference is made to FIG. 6 which discloses a portion of a heat-exchanger plate according to the invention as will be used in the several embodiments. This plate, represented at 100, is seen to have V-section corrugations 101 whose crests 102 lie in a plane 103 spaced away from the plane 104 from which the end 105 of the plate is bent in a quarter-round lip or flange. Thus, two confronting plates welded together will provide a semicylindrical dome for the chamber between the corresponding planes 104. The corrugations 101 are separated by troughs 106 open toward the plane 163 and away from the plane 104 while the crests 107 corresponding to these troughs terminate at the plane 10%. Similarly, troughs 108 between the latter corrugations open into the compartment defined between a pair of facing plates. The corrugations thus project from one side of the plates, here termed the reverse side, while no projections are seen except for the flange along the inner or obverse side of the plates.

The corrugations 101 and, consequently, the respective troughs ms, 108 run at angles 3 of about 45 to the main fluid-flow direction represented by the arrow A and designated by the arrows 15 and 17 in FIG. 1. In addition, the corrugations define angles a about 45 with the longitudinal edges of the plates which are of rectangular configuration. Hence each plate is rotated through about an axis parallel to either its longitudinal or narrow edge, and juxtaposed with another plate not so rotated, the bent flanges or lips 105 will meet and the corrugations will run with similar inclinations but opposite orientations so that the corrugations of one plate will run in an array approximately at right angles to the corrugations of the other plate. If two plate pairs are brought together in back-to-back relationship, i.e. with their respective reverse sides in contact, the mutual rotation of 180 between them will result in criss-cross arrays of corrugations such that each corrugation will cross the corrugations of the other plate at a plurality of contact points. The fluid passing in the main flow direction through these crossing arrays of corrugations will be deflected and perturbed to promote heat exchange.

Referring now to FIG. 1, it can be seen that the basic element of a heat exchanger according to the present invention is a stack of substantially identical, rectangular corrugated sheet-metal plates 1, 2, 3, 4 and 5, preferably composed of a material having a low corrodibility such as stainless steel or Monel metal. These plates may be constituted as described in connection with FIG. 6 and have edges 6, 7 which are bent through cylinder segments of 90 of arc so that pairs of plates can have their adjoining lips welded or soldered together at seams 8 and 9 in the longitudinal direction. Plates 1 and 2 are paired to define compartment 18 and plates 3 and 4 are paired to define compartment 19. The plates 2 and 3 of the adjoining pairs contact each other in back.- to-back relationship and have their edges 10 and 11 sealed together as best seen in FIG. 2. Similarly, the edges 12 of plate 4 and the edges 13 of plate 5 are sealed together, preferably by welding. The plates 2 and 3 and the plates 4 and 5 thus contact one another along an imaginary common contact plane P or P along which the fluid is permitted to flow, as represented by the arrows 14, 15 and 16, 17. The plates 1 and 2 and the plates 3 and 4 define the flow compartment 18 and 19 through which other fluids may be passed.

Each plate 1 5 is geometrically identical to all the other plates but is rotated about an axis parallel to the main flow direction represented by arrows 14 16, through an angle of 180". within the compartments 18 and 19 and thus between the plates 1 and 2 and between the plates 3 and 4, we provide a plurality of spaced-apart stacks 24, 25 or 26, 27 of packing plates corrugated similarly to the plates 1 5 but of smaller rectangular dimensions and without, bent lips, as already described. Such stacks are thus provided between each pair of plates having spaced-apart (noncontacting) arrays of corrugations. In the embodiment illustrated, these stacks of packing plates consist of pairs of plates welded together in mutually facing relation-- ship. In FIG. 1, for example, one stack consists of mutually facing plates 28, 29 and 30, 31, the first pair (2%, 29) being in baclt-to-back relationship with the second pair (30, 31). Each pair of packing plates bears against the plane 104 (FIG. 6) of the interior of the compartmeat 18 or 19. The corrugations of all of the sheetmetal plates are substantially identical and run at an angle of 45 to the longitudinal or lateral edges of the rectangular plates whereby the corrugations of neighboring plates are mutually orthogonal and cross one another while the corrugations of one plate contact the other plate at a multiplicity of locations, thereby mechanically supporting the stack.

Thus it can be seen that the primary plates 1, 2, and 3, for example, form two separate neighboring plate pairs 1 and 2, 2 and 3 and these plate pairs form two separate compartments. One of the compartments is the compartment 18 and is provided with the stack of heat-storing plates 28 31. The other compartment is formed between the confronting and engaging reverse sides of the plates 2 and 3. The first compartment is open in the direction of arrows 14 and l5, while the second compartment must be provided with lateral inlets and outlets for flow in the direction of arrows 46.

In FIG. 2, we have shown a section and a plan view of a heat-exchanger assembly embodying the present invention and differing slightly from the heat exchanger in FIG. 1 although identical reference numerals are used to identify similarly functioning elements. In this embodiment, the primary plates 1 and 2 and the primary plates 3 and 4 are joined in pairs by edge bars 21 and 22 which sealingly connect the primary plates to define the regenerator flow compartments. Between each of the primary plates 1, 2 and the primary plates 3, 4, there is provided a secondary stack of heat-storage elements consisting of a single pair of plates 28a, 29a. The sealed edges of plates 1 and 2 are represented at 20 and 11, respectively, while the edges of the plates 3 and 4 are shown at and 12. In this case, the bars 21 and 22 are welded to the edges of the plates to define the compartments and to separate the compartments from one another.

The flow paths can be of the type shown in FIG. 1 by arrows l4 l7 and the stack of heat-exchanger plates in FIG. 2 can be seen to define flow cross-sections 32 37 and 38 43. Arrows 44 46 of FIG. I also demonstrate the flow of fluids for the various compartments represented at 47 56. In the embodiment of FIG. 2 as in the embodiment of FIG. 1, the primary plates and the secondary plates are corrugated as described generally with respect to FIG. 6, with the corrugations extending at angles of 45 to the flow direction and to the edges of sides of the rectangular plates. Since each crossover point of the corrugations of adjacent plates, which lie in orthogonal arrays, is defined by a pair of corrugations at right angles to one another and compressive forces are applied perpendicular to the plates and the corrugations, the entire assembly is highly compact and rigid, the corrugations providing additional structural strength and bending resistance.

In FIGS. 3 5, we have shown a heat exchanger receiving the stacks of plates and forming a regenerator block for an air rectification installation of the LINDE- F RANKL type. The heat exchanger thus serves for heat transfer between one or more pure gases, e.g. pure oxygen and/or pure nitrogen, which are not to be contaminated, and interchangeable streams of impure gas (e.g. impure nitrogen or some other sparging gas) and a crude gas such as air. The various fittings, conduits and manifolds described hereinafter thus function as means for feeding the several gases to the respective flow cross-sections. In this heat exchanger, the primary plates 1 5 etc. define respective compartments in pairs which receive the secondary stacks of corrugated plates 24 27 etc. already described. The assembly is generally a rectangular parallelepiped and is received in a generally rectangular paralellepipedal housing 61. The flow paths running in the direction of arrows l4 17 and the partition walls 62 64 extending in this direction maintain separations between the fluids of high purity which traverse these flow paths through the heat exchanger. At opposite ends, the housing 61 is formed with semicylindrical domes 65, 66 for feeding fluids to the heat exchanger and recovering it therefrom (FIG. 5), these domes being further subdivided by the partitions 62 and having inlet fittings 67 70 or outlet fittings 71 74 (see FIG. 4). individual fluids can thus be supplied through the inlet and outlet fittings and the respective compartments may be dimensioned in accordance with the relative volumes of the gases.

A further flow path through the heat exchanger extends from an inlet fitting 75 of a semicylindrical distribution dome 76 through the compartment 19a of the stack via the passages 77 thereof and then via an opening 78 into a collection dome 79 and its outlet 80. A further generally similar flow path is provided, as best seen in FIG. 5, from an inlet pipe 81 and its semicylindrical distribution dome 82 through corresponding openings, not shown, through a compartment 18a of the stack which is parallel to the compartment 19a. The fluid can be collected in a dome 83 and delivered to an outlet 84.

We also prefer to provide two additional similar flow paths between, for example, a pipe 85, the distribution dome 86, the plate stack, the collection dome 87 and a pipe 88 (FIG. 3) and between a pipe 89, a collection dome 90, flow passages in the stack and the dome 91 with its fittings 92. Plate-type heat exchangers of the aforedescribed type have the principal advantage that a wide variety of switching possibilities exists between the flow passages and the use of the heat exchanger can be adjusted to be an optimum for any thermodynamic conditions. Thus, for example, between the fittings 67 and 7 l or 68 and 72 or 69 and 73 or 70 and 74 different partial streams of fluids can be passed in simultaneous indirect heat-exchanging relationship. The ratio of this total flow cross-section for any particular fluid, constituting the sum of the individual partial cross-sections to the total flow cross-section for another fluid may be established in accordance with the relative volumes of these fluids. The partitions 62 64 etc. are advantageously adjustable to vary the crosssections.

When the system of FIGS. 3 5 is used as a regenerative heat exchanger, for an air-rectification installation, pure oxygen or pure nitrogen or both (through separate flow paths) may be introduced at the cold end of the heat exchanger through inlets 67 70 while the warm pure product is recovered at outlets 71 74. The cold is transferred by conduction through the primary plates to the stacks of secondary plates 24 27. Through the chambers containing these heat-storage masses, the impure gas, e.g. air, is fed to cool the air and precipitate impurities from it during one half-cycle while the chamber can be evacuated and sparged with a further gas during another half-cycle to remove these impurities. The flow paths through the regenerator compartments are thus provided with the aforementioned fittings 75 and 80, 81 and 84, 85 and 88 and 89 and 92. If the impure gas or air is fed to two of the compartments by inlets 75 and 81, the sparging gas may be passed through the other two compartments in the opposite direction via inlets 88 and 92. In this case, the partition 63 etc. between the respective sections of the distribution domes must be pressure-tight.

The stack of plates can also be provided such that the plates between the adjoining compartments 18 and 19 are sufficiently pressure-tight as to allow the impure gas or air to pass from inlet '75 to outlet 80 while the sparging gas is passed from inlet 84 to outlet 81, i.e. in countercurrent in adjoining compartments. Precautions may be taken for pressure equalization over the length of the heat exchanger although generally these are not necessary because of the manner of stacking as previously described.

it should be apparent that the heat-storage masses need not only be disposed within pairs of primary plates defining the compartments, but may also be positioned between pairs of plates. The gases traversing the heatstorage masses can pass linearly through the stack while the pure gases can pass laterally therethrough, and fittings may be provided at any level to recover gas of the desired temperature, e.g. to be supplied to an expansion turbine. The system allows the heat-exchange surface area to be increased at one side relative to the other and also enables the flow cross-section to be increased at the warmer end of the heat exchanger to accommodate the increased volume resulting from warming of the gas.

We claim:

1. A regenerative type heat exchanger,'comprising:

housing means defining a space and provided with inlets and outlets for conducting at least two fluids through said space;

an assembly of mutually parallel substantially coextensive corrugated primary plates having opposite parallel edges turned toward and welded to a respective edge of another primary plate and forming a pair therewith, the plates of each pair being spaced apart and parallel to one another between the welded edges to form compartments traversable by one of said fluids, each of said pairs of plates being direct in contact with the primary plates of adjoining pairs and defining therewith passages traversable by the other of said fluids, and respective stack of mutually coextensive corrugated secondary plates forming heat-storage reservoirs and each wholly received in a respective one of said compartments inwardly of the welded edges of the primary plates thereof, the crests of the corrugations of adjacent secondary plates of each stack bearing upon another and the crests of the corrugations of the primary plates of each pair bearing upon the crests of corrugations of the secondary plates at the outer sides of the respective stack within each compartment.

2. The heat exchanger defined in claim 1 wherein said primary plates are sealed in stacked relationship along edges other than the first-mentioned edges by bars interposed between and welded to the primary plates.

3. The heat exchanger defined in claim 1 wherein all of said secondary plates are geometrically identical and the secondary plates of each stack contact one another in front-to-back relationship, and the primary plates of said assembly are geometrically identical with alternate plates facing in opposite directions.

4. The heat exchanger defined in claim 3 wherein said corrugations lie at angles of substantially 45 to the edges of the respective plates and said plates are all substantially rectangular, the crests of the corrugations of plates in contact with one another running in mutually orthogonal relationship.

5. The heat exchanger defined in claim 4 wherein said housing includes a dome extending along one side of said assembly and provided with a plurality of inlet fittings, and partition means for subdividing said dome to form individual distribution chambers selectively communicating with said compartments.-

6. The heat exchanger defined in claim 4 wherein said edges turn toward each other of said primary plates and have quarter-cylindrical configurations.

7. The heat exchanger defined in claim 6 wherein the crests along inner faces of the primary plates defining each compartment lie in respective planes between which the respective stack of secondary plates is sandwiched, the corrugations of said primary plates projecting outwardly away from the respective planes into direct contact with the oppositely projecting corrugations of the primary plates of an adjacent pair. 

1. A regenerative type heat exchanger, comprising: housing means defining a space and provided with inlets and outlets for conducting at least two fluids through said space; an assembly of mutually parallel substantially coextensive corrugated primary plates having opposite parallel edges turned toward and welded to a respective edge of another primary plate and forming a pair therewith, the plates of each pair being spaced apart and parallel to one another between the welded edges to form compartments traversable by one of said fluids, each of said pairs of plates being direct in contact with the primary plates of adjoining pairs and defining therewith passages traversable by the other of said fluids, and a respective stack of mutually coextensive corrugated secondary plates forming heat-storage reservoirs and each wholly received in a respective one of said compartments inwardly of The welded edges of the primary plates thereof, the crests of the corrugations of adjacent secondary plates of each stack bearing upon another and the crests of the corrugations of the primary plates of each pair bearing upon the crests of corrugations of the secondary plates at the outer sides of the respective stack within each compartment.
 2. The heat exchanger defined in claim 1 wherein said primary plates are sealed in stacked relationship along edges other than the first-mentioned edges by bars interposed between and welded to the primary plates.
 3. The heat exchanger defined in claim 1 wherein all of said secondary plates are geometrically identical and the secondary plates of each stack contact one another in front-to-back relationship, and the primary plates of said assembly are geometrically identical with alternate plates facing in opposite directions.
 4. The heat exchanger defined in claim 3 wherein said corrugations lie at angles of substantially 45* to the edges of the respective plates and said plates are all substantially rectangular, the crests of the corrugations of plates in contact with one another running in mutually orthogonal relationship.
 5. The heat exchanger defined in claim 4 wherein said housing includes a dome extending along one side of said assembly and provided with a plurality of inlet fittings, and partition means for subdividing said dome to form individual distribution chambers selectively communicating with said compartments.
 6. The heat exchanger defined in claim 4 wherein said edges turn toward each other of said primary plates and have quarter-cylindrical configurations.
 7. The heat exchanger defined in claim 6 wherein the crests along inner faces of the primary plates defining each compartment lie in respective planes between which the respective stack of secondary plates is sandwiched, the corrugations of said primary plates projecting outwardly away from the respective planes into direct contact with the oppositely projecting corrugations of the primary plates of an adjacent pair. 